Background. Reproductive biology and the evolutionary constraints acting on dispersal stages are poorly understood in many stony coral species. A key piece of missing information is egg and sperm gene expression. This is critical for broadcast spawning corals, such as our model, the Hawaiian species Montipora capitata, because eggs and sperm are exposed to environmental stressors during dispersal. Furthermore, parental effects such as transcriptome investment may provide a means for cross- or trans-generational plasticity and be apparent in egg and sperm transcriptome data. Methods. Here, we analyzed M. capitata egg and sperm transcriptomic data to address three questions: (1) Which pathways and functions are actively transcribed in these gametes? (2) How does sperm and egg gene expression differ from adult tissues? (3) Does gene expression differ between these gametes? Results. We show that egg and sperm display surprisingly similar levels of gene expression and overlapping functional enrichment patterns. These results may reflect similar environmental constraints faced by these motile gametes. We find significant differences in differential expression of egg vs. adult and sperm vs. adult RNA-seq data, in contrast to very few examples of differential expression when comparing egg vs. sperm transcriptomes. Lastly, using gene ontology and KEGG orthology data we show that both egg and sperm have markedly repressed transcription and translation machinery compared to the adult, suggesting a dependence on parental transcripts. We speculate that cell motility and calcium ion binding genes may be involved in gamete to gamete recognition in the water column and thus, fertilization.
Bibliographical noteFunding Information:
This work was supported by grants from the US National Science Foundation (NSF OCE IEP 1756616 to Debashish Bhattacharya and NSF OCE, IEP, EPSCoR 1756623 to HMP), the Israeli Binational Science Foundation (BSF 2016321 to Hollie Putnam and Tali Mass), and the Paul G. Allen Philanthropies. Debashish Bhattacharya was supported by a NIFA-USDA Hatch grant (NJ01170). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
The following grant information was disclosed by the authors: US National Science Foundation: NSF OCE IEP 1756616, NSF OCE, IEP, EPSCoR 1756623. Israeli Binational Science Foundation: BSF 2016321. NIFA-USDA Hatch: NJ01170.
© 2020 Van Etten et al.
- Coral dispersal
- Coral gene expression
- Coral genomics
- Coral spawning
- Coral sperm and egg function
- Montipora capitata
ASJC Scopus subject areas
- Neuroscience (all)
- Biochemistry, Genetics and Molecular Biology (all)
- Agricultural and Biological Sciences (all)